Bryan Garner offers this Quote of the Day:
This is the long, twilight struggle between descriptivists and prescriptivists.
Descriptivists, who hold that language is whatever people do from time to time, must win in the end.
But prescriptivists, who hold that language rules should be observed, must fight a never-ending rearguard action, yielding ground slowly and reluctantly.
I am a prescriptivist at heart.